System and apparatus for delivering feed water to steam boilers



Dec. 4, 1934.

J E. HOLVECK SYSTEM AND APPARATUS FOR DELIVERING FEED WATER TO STEAM BOILERS 2 Sheets-Sheet 1 drum INVENTOR.

JJW' A TTORNE Y3 I at Filed April 11, 1932 1: 75 steam {mp and A s. M

Dec. 4;, 1934.

J. E. HOLVECK v SYSTEM AND APPARATUS FOR DELIVERING FEED WATER TO STEAM BOILERS Filed April 11, 1932 2 Sheets-Sheet 2 w an any 5 v R Y W mm m A Wm 7 x Patented Dec. 4, 1934 SYSTEM AND ArrARA'rUs FOR. DELIVER- TING FEED WATER T STEAMBOILERS Joseph E. Holveck, Grafton, Pa., assignor to The Aldrich Pump Company,

Pennsylvania, 7 Application April 11, 1932, Serial No. 604,370] r g 1 Claim. (01. 103-40) This invention relates to steam boilers, and more particularly to feed water pumping systems therefor.

An object of this invention is the provision of a feed water pump system for boilers that shall be simple in construction, efiicient and reliable in operation, and inexpensive to maintain in operating condition. I

Another object of the invention is the previ- 1 sion of a boiler feed pump system embodying a constant speed pump and means adapted to automatically vary the capacity of the system in accordance with the demand for feed water.

A further object of the invention is the provision of a pump system in which the pressure at which the feed water is delivered to the boiler or boilers may be automatically regulated to compensate for variations inthe back pressures exerted by the boiler on the incoming feed water.

Astill further object of the invention is the f provision of a feed pump system, having a constantjspeed pump, so arranged that by means of standardised water regulators; the capacity of the system and the pressure of the feed water and accumulator;

' the demand for feed water.

may be varied automatically in accordance with Other objects of the invention will, in part,pe apparent and will, in part, beobvious from the following. description taken in conjunction with i the accompanying drawings, in which:

Fig. 3 is a View in side elevation, partly in section of the pump valve chamber and apump loading and unloading mechanism;

Fig. 4 is a top plan view of a double-throw clutch embodied in the pump unloader of Fig. 3;

Figs. 5 and 6 are views showing the relative position of cams embodied in the pump unloader; Fig. 5, representing the unloading posi- ,5 tions; and Fig, 6 theloading positions thereof;

Fig. 7 a view, partly in section,.of a boiler feed water regulator embodied in the system of Fig. 8 is a View showing graphically the action of the pump unloader;

Fig. 9 is a graphic representation of the power input to, the pump when loaded and unloaded; Fig. 10 shows graphically the flow of water to the boilers as affected by the pump accumulator;

and the a corporation of Fig- 11 is a graphic representation of-the variation in loading and unloading time periods,

. of the pump and the total time of each cycle;

and

Fig. 12 is a. view showing a different location of the accumulator with relation to the boilers and a modified remote control system for the pump loading and unloading mechanism.

Throughout the drawings and the specification like reference characters indicate like parts.

Referring to Fig. 1 of the drawings, steam boilers land 2 are shown that deliver steam to a steam line or header 3.

Feed water is delivered to the boilers by means of a pump 4. The feed water is pumped from a feed water heater (not shown) through a main line 5 and branch linesfiland 7 into boilers 1 and 2, respectively.

While two boilersare shown, it is to be understoodthat, in the practical application of the invention, the number of boilers supplied with feed water is immaterial except as it affects the size or capacity of the pump. Each feeder or branch line has a valve 8 therein which is under the control of water: level responsive means 9 of any standard or known form suitable for the purpose.

A description of valve 8 and the water lever responsive means 9 is given in connection with the description of Fig. '7. In general, if the water level in the boiler falls to or below level o, va1ve 8 will be opened wide toits maximum open position and if the' water level rises. to or above level 0, valve 8 will be completely closed. For intermediate water levels, valve 8 will be adjusted to a corresponding position somewhere between its open and closed positions. Under ordinary conditions of operation the water level will besubstantially constant at level n.

Pump 4 shown in Fig. 1 may be any standard form of pump suitable for boiler feed water service. The particular pump illustrated is a triplecylinder single-acting pump. This type of pump is preferred because it is particularly adaptable for high pressure, even flow and high eificiency. The pump may be driven by means of an electric motor designed to operate at constant speed. The motor, as shown, is coupled to the crank shaft of the pump by means of a pinion and gear. The pump may also be driven by means of a steam engine or steam turbine running at constant speed.

Since the pump is driven atconstant speed, it follows that it will deliver at its" maximum capacity rate at all times when loaded. However,

since the demand for feed water is a variable depending upon the load which the boilers must carry, it follows that the pump system must be so controlled that such variable demands for feed water may be satisfied.

In order to satisfy variable demand conditions, the pump is loaded and unloaded in such manner that the rate at which feed water is delivered to the boilers will be substantially equal to the rate at which the water is evaporated and converted into steam.

In order that there shall be a continuous flow of feed water to the boilers during the periods in which the pump is unloaded; an accumulator 10 is provided. The accumulator comprises a cylinder 11 having a piston 12 therein. The piston is provided with a piston rod 13 that extends upwardly through the cylinder head 14.

The upper end of the cylinder is connected to main feed water line 5 and the lower or opposite end is connected by a pipe 15 to the steam header 3. Thus, the piston rod side of the piston is subjected to the discharge pressure of the pump and the other side thereof is subjected to the boiler steam pressure. Since the area of the piston rod reduces the effective area of the side of the piston subjected to feed water pressure, the area of the piston and rod are so proportioned, that, when the pump is loaded, the total pressure exerted by the feed water exceeds the total pressure exerted by the steam on the piston, and, when the pump is unloaded, the total pressure exerted by the steam on the piston exceeds the total pressure exerted by the feed water. Thus, the piston will move back and forth in accordance with the differential between the feed water pressure and the steam pressure.

If the piston is in the position shown in Fig. 1 and the pump is loaded, a portion of the feed water will be diverted into the cylinder on the top side of the piston. The pressure in pounds per square inch, of the feed water is such that the total pressure acting on the top side of the piston exceeds the total pressure of the steam acting on the bottom side of the piston, so that the piston will be forced downwardly in the cylinder. The rate at which the piston moves downwardly is dependent upon the extent to which the feed water regulator valves 8 are open because the cylinder 11, the feed water lines 5, 6, and 7, and the boilers are connected in parallel and the division of flow between the cylinder and the boilers will be inversely proportional to the resistance offered to the flow of water to the cylinder and the boilers, respectively.

Naturally, if the water level is low and the regulator valves are open wide or nearly so, the resistance ofiered to the flow of water to the boilers is proportionately less than the resistance offered to the .flow to the accumulator. Or, if the water level is relatively high, and valves 8 are closed or nearly so, the resistance offered to the flow of water to the boilers is proportionately higher than the resistance to flow into the accumulator.

Therefore at low water levels, the loaded periods of the pump will be longer and the unloaded periods shorter than when the water level is at or above the desired value, as will be explained in connection with the graphs shown in Fig. 11.

When the piston reaches the bottom of the cylinder or some predetermined point in itsdownward stroke, a lug l5 on'the piston rod engages and shifts a'lever lfiwhich in turn operates mechanism that unloads the pump. When the pump is unloaded, the pressure in the feed water line drops slightly so that the total pressure of the steam acting on the underside of the piston will be sumcient to force the piston upwardly and discharge the water stored therein into the main feed water line and the branch lines to the boilers. Thus a constant flow of feed water to the boilers is maintained while the pump is unloaded.

When the piston reaches the end of its upward stroke or some point in its upward stroke, lug 15 engages a lever 1'7 that operates the mechanism to pump loading position. The pump being loaded again, feed water is delivered to the boilers and to the accumulator, as above described, at rates which are fixed by the resistance to flow in the respective parallel branches.

Since the extent to which the feed water regulator valves 8 are open is dependent upon the water level in the boilers and hence fixed by the demand for feed water, it follows that the rate at which the accumulator isv charged, when the pump is loaded, and the rate at which it is discharged under the action of steam pressure, when the pump is unloaded, will vary automatically with the demand for feed water.

Therefore, it follows that the length of the loading and unloading periods of the pump in seconds or minutes will vary automatically in accordance with the demand for feed water. Also, since the pressure at which the feed water is delivered by the pump into the main feed water line is dependent upon the pressure exerted by the boilers against the entry of feed water, it is apparent that the pressure of the feed water will also vary automatically in accordance with the pressure in the boiler.

For any given steam pressure at which the boilers are designed to operate, the pressure at which the feed water is delivered by the pump to the feed water line, will exceed the pressure of the steam in the steam header 3 by a predetermined amount, say 50 pounds per square inch. This differential will be maintained since as explained above the discharge pressure of the pump will vary automatically with variations in the steam pressure, and will always be a definite amount higher than the steam pressure.

If, for example, the boilers shown require a combined maximum demand of gallons per minute, a pump having a capacity of 190 gallons per minute operating under load continuously will satisfy. If the demand by the boilers falls to say 90 gallons per minute, and if it be assumed that the accumulator has a displacement capacity of 7 gallons, this demand will be satisfied if the pump is operated under load for 45 seconds and unloaded for five seconds. In such a case, the output of the pump while loaded, will be at the rate of gallons per minute, and this output will be delivered to the boilers at a rate of 90 gallons per minute and to the accumulator at the rate of 10 gallons per minute. Thus, at the end of 45 seconds, the boilers will have received 67 gallons and the accumulator 7 gallons. water received by the accumulator will be displaced into the boilers, when the pump is unloaded, during the unloading period of five seconds, at the rate of 90 gallons per minute or 1 gallons per second. When the accumulator is unloaded, the pump is reloaded, so that at the end of a minute a total of 90 gallons will have been delivered to the boilers. The accumulator always takes a charge of 7 gallons, before the pump is unloaded, and the time required to charge The the accumulator with 7% gallons will depend upon the extent ofopening of the regulator valves 8, which in turn is dependent upon the water level in theboilers.

If the water level inthe boilers is low, valves 8 will be open relatively ,wide andthe pump will operate underload for a relatively long period of time because the resistanceoffered to the flow of water to the boilers isless than to theaccumulator. If thevalves are near their closed positions, the resistance offered to the flow of water to the boilers will be relatively high as compared to the resistance to flow to the accumulator,

therefore, theaccumulator will be charged at a higher rate. In the first case, the pump will be loadedfor a relatively long period of time and unloaded for a relatively short period of time;

and in the latter case the pump will be loaded for vary with the demand; and curve 20 shows'how the total time involved in each cycle of operation (where each cycle includes one loaded and one unloaded period) varies with the demand.

Unloading mechanism The unloadingmechanism operates on the suction valves 21 of thepump, there being three suction valves,.one for each pump cylinder. This mechanism, when shifted to position L by the piston rod lug 15 and lever 17, renders the suction valves operative! so that they may function in their normal manner and cause the pump to deliver feed water to the boilers and the accumulator as described previously herein. When shifted to position U by the piston rod lug and lever 16, the suction valves. are rendered inoperative, and the pump is unloaded.

The loading and unloading mechanism is operated in synchronism with the pump crank shaft 22, so that the suction valves are rendered either operative or inoperative during the suction strokes of the r respective pistons of the pump. Thus, unloading :of the pump always occurs at the end of the discharge strokes of the pump pistons, and loading takes place only at the beginning of the discharge strokes thereof.

Fig. 8 graphically illustrates the operation of.

the unloading. mechanism. In this figure curves A, B and C,.which-are sine curves disposed 120 apart, representthe discharge and suction impulses of the respective pump pistons. The positive portions of the curves represent the discharge impulses of each pump piston and the negative portions thereof represent the. suction impulses. When the suction valves are in their operative positions, the pump delivers the water to the boilers and the accumulator asindicated by section d of the curve. Whenthe suction, valves are actuated to their inoperativerpositions, the discharge impulses disappear because the suction valves are held open so that. anywater taken into the cylinders is displaced orreturned into the suction line of the pump. The unloaded condition of the pump is represented by section eof the curves. As soon as the pump is loaded again the suction and discharge impulses appear as represented by section 1.

While the pump is unloaded nowork is done, so that the power input to the motor is only sumcient to overcome the mechanical losses of the pump which amounts to aproximately 8% to 10% of the normal power as illustrated graphically by curve 23 shown in Fig. 9. When the pump is loaded, the powerinput to the motor is represented by section 2' of curve 23 and when unloaded, the poweririput drops off gradually to a valve represented by section ;i of the curve, because the pump discharge decreases at this point in accordance with the sine curves of Fig. 8. While the pump is unloaded the power input to the motor is only suflicient to overcome mechanical losses of the pump. When the pump is loaded, the power input to the motor increases gradually in accordance with the sine rate of increase in the discharge from the pump.

Fig. 10 represents graphically the flow of feed water to the boilers during the loading and unloadingperiocls of the pump. When the pump is loaded the discharge from the pump is divided between the boilers and the accumulator. When the pump is unloaded and the discharge therefrom is approaching Zero, the accumulator begins to discharge into the boiler and maintains the flow until the pump is loaded. As soon as the pump is loaded, the flow therefrom gradually increases, the flow from the accumulator gradually decreases to zero, afterj'which water flows into the accumulator. r V

From the graphic illustration of Fig. 10, it will be apparent that the flow to the boiler is practically constant. I f r The unloading mechanism may take various forms, but the one illustrated in Fig. 4 may be utilized as it effectively performs the functions intended. The unloading mechanism comprises a shaft 25 on which earns 26, 27, and 28 are mounted. The cams as shown,aredisposed 120 apart in time relation to the pump crank shaft 22 (see Figs. 5 and 6) and are arranged to actuate the suction valves in the order indicated by the sine curves of Fig. 8 which represent the pump suction and discharge impulses of the pump.

.The cams operate rocker arms 29, 30, and 31 upon which the valve stems 32, 33, and 34 of the suction valves rest. If the cam shaft isturned 180, so that the rocker arms rest on the high or raised portions of the cams (see Fig. 5) the valve stems and the valves will be lifted upwardly and held in their inoperative. positions. The cam shaft is turned 180 during the suction strokes of the pump pistons. p

By turning the cam shaft in the same direction 180? the cams will occupy such positions that the rockerarmswill rest on dips of the cams (see Fig. 6) thereby returning or releasing the suction valves to their operative positions. The cams are turned to this position during thesuction strokes of the pump pistons so that the pump cylinders will be loaded at the beginning of their discharge strokes. r 1

In order that the camshaft may be connected to the phmpcrank shaft and turned 180 at a time and in synchronism with the crank shaft, a double-throw clutch is provided. The doublethrow clutch. is shifted to pump loading position or to pump unloading position by means of levers 16 and 17 which operate a connecting rod 36. One end of the connecting rod is coupled to a bell crank 3Tithat operates the double-throw clutch to is turned 180 in the direction of arrow 50 thereby Til its pump loading or pump unloading positions L and U, respectively.

The double-throw clutch comprises apinion 38 which is turnably mounted on a shaft 39 coupled to cam shaft 25. A rack 40, that meshes with the pinion, is coupled, by means of a connecting rod 41, to a crank 42 secured to one end of the pump crank shaft. Thus, as the pump crank shaft rotates, the connecting rod and the rack reciprocate thereby turning the pinion forwards and backwards in synchronism with the pump crank shaft 22. The stroke of the connecting rod 41 and. the rack is such that the pinion will turn 180 in either direction.

Keyed to, but slidably mounted on shaft 39 on each side of the pinion are clutch members 44 and 45 having lugs 46 and 47 thereon adapted to engage, respectively, dogs 48 and 49 formed on opposite sides of the pinion. The dogs on the pinion are so shaped that they will engage the lugs on the clutch members only when the pinion is turning in the direction of arrow 50. The clutch members are tied together by means of collars 51 and a tie rod 52 to the bell crank 37.

; :Thus, when the bell crank is turned counterclockwise, lug 47 on clutch member 45 will be shifted to position L, and be engaged by dog 49 on the pinion. Cam shaft 25 will, therefore, be turned 180 in the direction of arrow so that the cams :will occupy the relative positions shown in Fig. 6. When turned 180 to the position shown in Fig. 6,

the pump suction valves are released to their operative positions in the manner described above, and the pump is loaded.

When the accumulator has been charged with "a predetermined quantity of water, lug 15 on the piston rod engages lever 17 and turns bell crank 37 clockwise,-thereby shifting clutch member 44 to position U. When in this position the lug 46 engages dog 48 on the pinion and the cam shaft raising the rocker arms 29, 30, and 31 and actu- 'ating the suction valves to their inoperative positions, whereby the pump is unloaded.

Thus, by means of the accumulator and the feed water regulator valves 8, and the water level responsive means 9, and the unloading mechanism,

the pump may be loaded and unloaded automatically for such periods of time that the amount -of feed water delivered to the boilers will correspond to the demand therefor.

When the pump is operating under load, it is delivering at maximum capacity but it operates at maximum capacity only for such lengths of time as are required As the decrease and the unloading periods increase. Although the pump is unloaded for variable lengths of time and loaded for variable lengths of time,

-'there is a continuous flow of feed water to the boilers at a rate which corresponds to the rate of demand.

Since the pressure at which the feed water is delivered by the pump is dependent upon the back pressure against which the pump operates, it follows that the pressure of the feed water as delivered to the main feed water line will vary automatically with variations in the boiler pressure.

Feed water regulators The feed water control valve 8 and the water level responsive means 9 which operates the valve, utilized to control the rate of flow of feed water to the individual boilers are shown in Fig. '7.

-; While particular types of valve and water level responsive-means are shown, it is to be understood that other types of regulators and valves may be employed if desired. The type of regulator illustrated is a well known standard unit.

Since these regulators control the rate of charge and discharge of the accumulator and thereby determine automatically the length or duration of the loaded and unloaded periods of the pump, it is thought that their construction and mode of operation should be set forth herein.

Valve 8 comprises a valve body 52 having a valve disc 53 therein mounted on a valve stem 54. When the valve stem is moved downwardly, the valve disc moves away from the valve seat 55 towards open position. Upward movement of the stem moves the valve towards closed position.

The valve stem extends upwardly through a stufiing box 56 formed in a cover or cap 57. A

pair of studs 58 extend upwardly from the cover or cap 57 and carry a support 59 which may be raised or lowered with respect to the valve cap, by means of nuts 60 threaded on the studs. Support 59 acts as a reaction or abutment for a coil spring 62 disposed about a pusher rod 63, the lower end of which is attached to the upper end of the valve stem. The pusher rod carries a support or retaining member 64 which forms a bearing for the upper end of the spring.

A plate 65 is mounted on the upper end of the studs to which stud bolts 66 are attached for supporting a plate 67 to which a bellows 68 is secured. The lower end of the bellows rests on the upper end of the pusher rod.

Liquid, such as water is confined in the bellows and communicates, by means of a pipe or tube 69, with the water level responsive means 9. As the pressure of the water in the bellows increases, in response to a drop in the boiler water level, the pusher rod is moved downwardly against the action of spring 62 and opens the Valve. If the water level rises, the pressure in the bellows decreases causing the valve to move towards its closed position. As stated previously herein, spring 62 is so adjusted that when the water level falls to or below the level 0, the bellows will expand to such a point that the valve will be completely open. If the water level rises to or above level 0, the pressure in the bellows will be reduced to the point where spring 62 will completely close the valve.

The water level responsive means comprises an outer tube or shell '70 having cooling fins 71 thereon, and an inner tube '72 that extends through the outer tube. The opposite ends of the outer tube are secured in fluid tight relation on the inner tube by means of expansion heads 73 and 74.

The inner and outer tubes are disposed or inclined at an angle with the raised end connected to the steam space of the boiler at a predetermined point above the water level, and the lower .i

end is connected to the water space of the boiler at a predetermined point below the normal water level. A water leg '75 is interposed between the lowermost end of the inner tube and the connection to the Water space of the boiler. This water 3 leg has cooling fins thereon so that a column of cool water may be available to accelerate the condensation of steam in the outer tube when the boiler water level is rising.

The valve operating bellows 68 is connected by steam space and the water space of the boiler, 1;

the water will rise in the inner tube to the level of the water in the boiler. Thus, the inner tube will be partially filled with steam and water according to the level of the water in the boiler.

As the waterlevel in the boiler varies, the quantity of steam in the inner tube will vary. If the water level in the inner tube is lower than in the outer tube, some of the water in the outer tube will flash into steam.

The steam expands forcing water into the tube 69 and bellows 68 until the level of the water in the outer tube is equal to the level in the inner tube. The bellows is therefore subjected to an increase in pressure causing it to expand and open the valve in proportion to the pressure increase. If the water level in the boiler rises, the water level in the inner tube rises, causing steam in the outer tube to condense whereby the pressure therein is reduced, thereby relieving the pressure in the bellows 68. Upon a reduction in pressure in the bellows, the valve moves towards its closed position and the water level in tube 70 rises to the level in the inner tube '72. If the boiler water level rises to point 0 and the inner tube is completely full of water, the valve will be actuated to its closed position; and if the water level in the inner tube falls to point 0, the valve will be actuated to its wide open position.

As shown in Fig. 1, the accumulator is mounted in a vertical position on the base of thepump. In some cases it may be desirable tomount the accumulator, at a point above the boiler drums as shown in Fig. 1, either in a horizontal or in a slightly inclined position so that steam which condenses in the steam side of the accumulator may drain into the boiler. With the arrangement shown in Fig. 12, condensed steam must be drained off to a steam trap as indicated.

Where the accumulator is mounted above the boilers, as in Fig. 12, a solenoid '77 may be utilized to operate the double-throw clutch of the pump loading and unloading mechanism. The solenoid has a movable core '78 connected by a link 79 to bell crank 37, the link having a counterweight 80 thereon to shift the double-throw clutch to unloading position when the solenoid is deenergized.

When the water in the accumulator has been discharged, lug 15 on the piston rod 13 closes a normally open switch 82 whereby the coil of re-;

therefore through contact members 87, 88 and a bridging member 89 whereby the relay will remain energized until the normally closed switch" is opened. g

Relay 83 when energized also connects the solenoid 77 across the supply conductors through contact members 90, 91 and a bridging member 92.

While the accumulator is being charged, solenoid 77 remains energized until lug 15 opens the normally closed switch 85. When switch 85 is opened, relay 83 is deenergized, the holding circuit therefore being broken, and solenoid 77 is deenergized causing the double-throw clutch to be shifted to pump unloading position.

While a particular form or embodiment of the invention has been shown and describedherein, it is to be understood that various modifications and changes may be made inthe system without departing from the spirit or the scope of the invention. It is desired therefore that only such limitations shall be placed on the invention asare imposed by the prior art and the appended claim.

What I claim as new and desire to secure by Letters Patent is:

The combination with a boiler having a feed water delivery line connected thereto, a continuously driven pump connected to deliver water to said line, mechanism for loading and unloading the pump, and means for operating said loading and unloading mechanism, of a cylinder having a piston therein of substantial travel and displacement, a piston rod attached to one side of said piston providing differential piston areas, said piston rod being disposed to actuate said operating means to effect loading of the pump when the piston reaches the end of its stroke in one direction and to effect unloading of the pump when the piston reaches the end of its stroke in the opposite direction, a connection between said feed water line and cylinder placing the piston rod side of the piston in continuous communication with the feed-water line, a connection between said cylinder and the steam space of the boiler placing the opposite and larger side of the piston in continuous communication with said steam space, the piston travelling in one direction when the pump is loaded under the action of vwater pressure, and in the other direction under the action of steam pressure when the pump is unloaded, the pump, piston and cylinder cooperating to maintain a continuous flow of feed-water to the boiler, and means responsive to. changes in the boiler water level for varying thewater pressure developed by the pump in the feed-water lineand in the connection thereof to said cylinder to thereby vary the speed of travel of the piston in either direction, the length of time the pump is loaded and unloaded, and the rate of water delivery to the boiler in accordance with the boiler water level.

JOSEPH E. HOLVECK. 

